Advances in treating heavy metals containing wastes

A review is presented of progress made in the period between roughly 1980 and 1985 in treating wastewaters that contain heavy metals ions. The review concentrates on wastewaters from the metalplating industry. The applicability of electrodeposition has been greatly improved through the development of large surface area electrodes. Electrodeposition now appears to be a promising treatment method, especially for wastewaters that contain heavy metals ions in fairly high concentrations together with chelating agents. Water evaporation techniques and adsorption on insoluble starch xanthate are promising developments that merit attention. Heavy metals sulfide precipitation by adding compounds like FeS and CaS seems to be an improvement in comparison to older methods in which soluble sulfides were added. Ways to separate different species of heavy metals ions from each other by means of combined ion exchange and hydrometallurgical extraction may be of interest in situations were the wastewaters from many firms are treated in one central processing plant. Progress in membrane processes is to be expected as the quality of membranes steadily improves. Several other novel and interesting removal methods have been proposed such as e.g. electroprecipitation and the reduction of chromates with sulfides and ferrous ions.